toilet drain to vent pipe distance
I'm plumbing in a new bathroom (toilet/sink/shower). This bathroom backs up to an existing bath so most of my plumbing is pretty clustered. I have the sink going up a 1-1/2 inch vent and the shower with a 1-1/2 inch vent with the drain headed towards the toilet.
My question is: The new toilet is using a 4 inch drain and is 7 feet away from the the main vent stack which is also 4 inches in diameter. Is this vent sufficient or is it necessary to get a smaller vent closer to the new toilet drain?
My book says that with a 4 inch drain, the max distance to the vent is 10 feet, but I'm trying to make doubly sure as a 2 inch vent would end up swiss cheesing the (non-load bearing) 2x4 wall that separates the 2 bathrooms.
Thanks inadvance for yer help.